XI EXAMINATION OF MILK 195 



The preparation may be utilised to gain an idea of the 

 general bacterial content, if streptococci are present, and if so 

 in what numbers and whether intracellular, while, if con- 

 sidered necessary, a differential count may be made of the 

 cellular elements present. 



With care a rough but valuable estimate can be obtained 

 from this examination as to the probable number of bacteria 

 in the sample. In Chapter I. a description is given of the 

 different cells found in milk deposits. At least 200 leucocytes 

 should be enumerated. 



C. The Estimation of the Volume or Weight of 

 Sediment obtainable eeom Milk 



The amount of sediment in milk has been measured and 

 estimated by a number of observers, each worker using as a 

 rule his own method which, while giving comparable results 

 for his own work, renders comparison with the results of other 

 investigators useless. It may be said that there is no one 

 method which is generally accepted. The following are some 

 of the more important procedures which have been used in 

 this country : 



1. DeUpines Method} — Delepine estimates the sediment 

 from milk by measuring the diameter of the sediment deposited 

 in tubes of uniform diameter, each containing 40 c.c. of milk, 

 and left for a quarter of an hour in a centrifugal machine 

 running at the rate of about 2500 revolutions per minute. 

 The absolute amount of sediment is not indicated by these 

 measurements, but Delepine estimated the relationship between 

 the diameter and the weight of these sediments. In this 

 way he constructed an approximately reliable scale. 



2. Houston's Method? — A litre of milk is allowed to stand 

 (with 1 c.c. of formalin added to inhibit bacteria) in a long 

 tube with a narrowed, graduated lower portion provided with a 

 glass tap. The solid matters sink, and after 24 hours the 

 volume of sediment is read off on the scale. This Houston 

 calls the " primary reading." A centrifugal tube -with the 

 lower part graduated and of narrow bore is then held under 



^ Medical Chronicle, March 1908. 

 2 Report to the London County Council (No. 933), 1905. 



